package codingStudy.Dynamic.climbingStairs;

import java.util.Scanner;

/**
 * @author dell
 * @category
 
  
 */
public class Bate2 {

	private static int[] money;

	static int countStep(int x) {
		for (int i = 3; i < x + 1; i++) {
			money[i] = money[i - 1] + money[i - 2];
		}
		return money[x];
	}

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int tage = sc.nextInt();
		money = new int[tage + 1];
		money[1] = 1;
		money[2] = 2;
		System.out.println(countStep(tage));
		
	}

}
